Possum & Rat Bait Toxicities in Dogs

Possum and Rat Bait toxicities in dogs

Anticoagulant poisons

An anticoagulant bait is used to kill rodents and possums by preventing blood from coagulating (clotting), so that an animal will eventually bleed to death from internal or external bleeding. These baits are being used extensively in the Hawkes Bay for controlling possum numbers in many reserves, Te Mata Peak and DOC areas. In addition they are used to control rats and mice in household/orchard situations. They are also highly toxic to dogs, and as a vet I see numerous cases of poisoning every year. Unfortunately these baits are made attractive to their target pest using grains etc which also makes them attractive to dogs – especially more food orientated breeds such as Labradors! Poisoning is generally but not always, from eating the bait directly as opposed to eating rats/possums that have died from the bait.

There are various types of anticoagulant baits used, but the common ones are:

Brodifacoum eg Talon

Pindone

Diphacinone

Warfarin type substances such as coumatetralyl eg Racumin

Flocoumafen eg Storm

Warfarin type products require multiple feeds over several days to kill, but the other products are higher potency designed to kill with a single feed. Products containing Brodifacoum are 50-200 times more potent compared with wafarin and last in the system for up to 4 weeks.

Clinical signs

These baits work by blocking the synthesis of vitamin K, which is an essential component of the clotting process - causing spontaneous and uncontrolled bleeding. However, after access to the bait it generally takes 3-4 days for clinical signs of bleeding to start. This can be a problem as some owners catch their animal eating the bait and then assume it has no effect as the dog seems initially well, or alternatively notice their dog is unwell but not associate it with any bait access.

Dogs can present with many different signs depending on the site of the bleed, for example:

i) Bruising with blood filled swellings under the skin

ii) Bleeding from the nose, eyes, ears

iii) Red urine from bleeding into the bladder/kidneys

iv) Coughing/breathing difficulties from bleeding into the lungs/chest cavity

v) Bloody faeces/vomit from bleeding into the intestines

vi) Bleeding into cavities such as the abdomen causing a swollen belly

Blood loss eventually leads to signs of shock with pale gums, weakness, collapse and if untreated, death. It is more worrying if your dog bleeds into the lungs as they can die quickly from lack of oxygen, even before they loose too much blood.

If you know your dog has eaten any bait please take him/her to the vet as soon as possible - bringing details of the bait with you if available.

Diagnosis

Your dog will be initially thoroughly examined to check for signs of blood loss and shock. Then a blood test will be taken to check how long it takes the blood to clot to confirm access to the bait, and also to check how much blood has been lost. It’s amazing how many owners are unaware their dog has eaten bait.

Treatment

With most baits, if they have eaten them within the last 3-4 hours, your vet with give an emetic drug to induce vomiting to empty the stomach. However, your dog may still need a blood test in 2-4 days to check how quickly the blood clots, to ensure the bait has not been absorbed into the system. If you dog is already showing signs of bleeding and it is life threatening, they may initially need a blood transfusion. Then he/she will be given the antidote vitamin K, initially by injection. Your dog will then need to stay on oral vitamin K for the next 4 weeks. Your vet may need to monitor blood clotting time with further blood tests to check the treatment is working.